A power window system is a common accessory on a modern automobile. The system employs an electric motor coupled to a window regulator mechanism for opening and closing (e.g., lowering and raising) a window of the vehicle. The motor receives electrical power from the vehicle electrical system, and is coupled to a switch located within the vehicle and convenient to the vehicle operator. The motor is responsive to selective actuation of a switch to either drive the window regulator mechanism to move the window glass from closed positions to open positions and vice-versa. Typically, the vehicle operator presses and holds the switch in one of two positions for moving the window between open and closed positions.
A recent feature that has become common to motor vehicle power window systems is referred to as express or automatic open. In the past the vehicle operator had to press and hold the switch while the motor moved the window to the desired position. An automatic open function moves the window from any position to the full open position responsive to a single press of the switch and without holding the switch.
Still more recently, it has become desirable to provide an express or automatic close feature. This feature allows the window to be moved from any open position to the fully closed position with a single press of the switch and without holding the switch. Several vehicle manufacturers are now offering such a feature.
As will be appreciated, with this added functionality the power window system has become quite complex. Automated open functions must, for example, control the rate at which the window glass descends into the door to prevent damage to the regulator mechanism and to stop the motor when the window glass is in the fully open position. Automated close functions require detection of obstructions that might inhibit fully closing the window and provide an appropriate response. Of course the system must also detect when the window glass is in the fully closed position to stop the motor. Still further, the system must be able to detect failures that may effect system operation and particulary those failures that may effect automatic operation. Fortunately, the ability to provide affordable sophisticated control and diagnosis of the power window system is possible with the use of microprocessors and other associated electronic devices.
It is important to rapidly and reliably detect the operating conditions of the motor and to communicate these conditions to the electronic controller to allow it to quickly and properly control the motor' operation. With this in mind, it has been the practice to associate the control electronics directly with the motor allowing it to directly communicate with the motor using virtually any number of wired connections. This design substantially increases the size of the motor package. A motor including an electronic control module may occupy nearly twice the volume of the motor alone. Since the motor must be positioned in proximity with the window regulator mechanism, e.g., within a door of the motor vehicle, increasing the size of the motor presents problems. There are many competing interests in the design of an automobile. The vehicle stylist seeks visual appeal. The vehicle engineer seeks safety, function and durability. The vehicle marketer seeks ever more features, functions and performance. The vehicle designer is left balancing these competing interests. To provide flexibility to the designer, it is desirable to separate the electronics module from the motor. This allows the designer to position the now smaller motor package in the required position for proper operation of the window regulator mechanism while positioning the electronics at a more convenient location, i.e., where more space is available. Unfortunately, separating the relay device from the motor raises the problem of quickly and reliably communicating operating condition data from the motor to the controller and control signals from the controller to the motor. A parallel data link requires a significant number of wires, requires larger wire connectors, occupies more space and increases cost. A serial data link may not be fast enough or have enough bandwidth without incorporating sophisticated, and expensive, data transmission technology to carry all of the information necessary to ensure proper motor operation.
Thus there is a need for an improved automatic power window system.